Toroidal-like saddle yoke

ABSTRACT

A deflection yoke for a color television picture tube includes a saddle-type winding wound directly on a magnetic core. The core is provided with slots on each end, formed either directly in the core material or by attaching slotted rings to each end of the core, such that each turn of the winding formed on the core may be exactly positioned along the inside surface of the core by stretching the wire between corresponding slots on opposite ends of the core. End turns are formed contemporaneously with the winding by running the wires annularly about the outside surface of the core between respective exiting and re-entry slots for each turn.

Logan et al.

TOROlDAL-LIKE SADDLE YOKE inventors: James H. Logan; Bennie A.

Findeisen, both of Baldwinsville; Wilfred Rublack, Liverpool, all of NY.

General Electric Company, Syracuse, N.Y.

Filed: Dec. 6, 1974 Appl. No.: 530,189

Related [1.8. Application Data Continuation-impart of Ser. No. 426,328, Decv I9, I973, abandoned.

Assignee:

US. Cl 335/210; 335/2l3 Int. Cl. H0 7/00 Field of Search 335/210, 2l3; 313/421,

References Cited UNITED STATES PATENTS Leeds..... ass/2:3 x Corpew 335/213 [451 July 15, 1975 3,60l,73l 8/l97l Christiana et a] 335/213 X FOREIGN PATENTS OR APPLlCATlONS 624,584 7/1961 Canada 313/76 Primary ExaminerG. Harris Attorney, Agent, or Firm-Marvin Snyder [57] ABSTRACT A deflection yoke for a color television picture tube includes a saddle-type winding wound directly on a magnetic core. The core is provided with slots on each end, formed either directly in the core material or by attaching slotted rings to each end of the core. such that each turn of the winding formed on the core may be exactly positioned along the inside surface of the core by stretching the wire between corresponding slots on opposite ends of the core. End turns are formed contemporaneously with the winding by running the wires annularly about the outside surface of the core between respective exiting and re-entry slots for each turn.

7 Claims, 3 Drawing Figures 1 TOROIDAL-LIKE SADDLE YOKE This is a continuation in part of our copending application Ser. No. 426,328, filed Dec. l9, 1973 now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a magnetic deflection yoke for a cathode ray tube. and more particularly to a saddle-type yoke wound directly on the yoke core, and a method of making such yoke.

Deflection yokes for cathode ray tubes are generally of toroidal or saddle-type construction. Toroidal yokes are usually constructed by winding a number of turns of a conductor about a sleeve or toroid in a direction essentially parallel to the axis of the toroid resulting in a layer of conductors on the inside surface and a corresponding layer on the outside surface of the toroid. Saddle windings, so called because of the saddle-like configuration of the winding, are formed by relatively complex machinery into an approximately saddleshaped coil comprising numerous, randomlypositioned turns of a conductor, and the coil is then manually or mechanically pressed into the final saddle configuration.

The toroidal yoke has certain advantages over a saddle-yoke. For example, because the toroid is wound directly into its final position on a core, it is cheaper and easier to wind and each turn of a winding can be accurately positioned by winding from a designated point on one end of the toroid to a corresponding point on the opposite end. Accurate positioning of the individual turns means that control of the impact point or final raster position of an electron beam can be more easily implemented without requiring elaborate driving circuitry to correct for electron beam geometrical errors caused by inaccurate winding placement. In addition, accurate placement of each winding turn means that a small number of turns are required; i.e., since each turn is precisely positioned, it is allowed to have greater effeet on the electron beams. This is sometimes referred to as giving each turn more magnetic weight. Fewer turns result in lower impedance. thus making a toroidal yoke ideal for solid state driving circuitry which commonly exhibit low output impedance.

On the other hand, the toroidal yoke manifests an extended field of higher amplitude than the saddle yoke and a yoke-region field of lower amplitude than that of the saddle yoke; i.e., for the same core size the flux density in a toroidal yoke is higher in the extended field and lower in the yoke region than the flux density in a saddle yoke. This higher flux density to the rear of the toroidal yoke requires that electron beam deflection be greater near the rear of the toroidal yoke than near the rear of the saddle yoke to achieve the same final deflected beam impact position. In applications where beam deflection of no more than 70 to 90 is required, early large deflection of the beams is tolerable. However, in wide-angle cathode ray tubes beam deflection may be required at angles greater than 100. At these larger angles a phenomenon commonly referred to as neck shadow begins to occur. Neck shadow is the result of the beam being deflected at a large angle at such an early point in the beam trajectory that it intersects the neck of the cathode ray tube and is thereby prevented from reaching the screen. With a toroidal yoke the neck shadow problem can be overcome by shortening the rear extension of the core so as to move the rear extended field forward in the tube; however, to accomplish the same deflection with a shorter core requires considerably more driving current to obtain a higher field intensity, resulting in a loss of efficiency.

The saddle-type winding is advantageous in that it provides a means of minimizing the neck shadow problem. In a saddle-type winding flux density is concentrated in a smaller volume and, as a result, beam deflection begins at a more forward location in the tube. thus allowing for a wider deflection angle with a given length core than is possible with the same length core in a toroidal yoke. In addition, saddle-type windings. because of the more concentrated flux density. tend to be more sensitive than toroidal windings for equivalent deflection angles.

Saddle-type windings, however, require complex winding and forming equipment with attendant increased manufacturing cost. Moreover, because the windings are wound without a core and are later shaped, the position of individual turns is only randomly defined, thus requiring that the windings be formed of numerous turns, each of relatively small magnetic weight." Numerous turns make saddle-type windings high impedance devices generally unsuitable for use with a low impedance deflection circuit.

Accordingly, one object of the present invention is to provide a cathode ray tube magnetic deflection yoke having the low impedance and accurate winding placement capabilities of a toroidal yoke and the high sensitivity of a saddle-wound yoke.

Another object is to provide a toroidal-like magnetic yoke for deflecting electron beams in a wide angle cathode ray tube without producing neck shadow.

Another object is to provide a toroidal-like deflection yoke for a cathode ray tube wherein magnetic flux is concentrated in a relatively small volume.

Another object is to provide a method of fabricating a saddle-wound toroidal-like deflection yoke for a cathode ray tube.

SUMMARY OF THE INVENTION Briefly, in accordance with a preferred embodiment of the present invention there is provided a deflection yoke for a cathode ray tube in which a winding of saddle-type configuration is wound directly on a core. Preferably the core is formed with suitable castellations or slots on each end so that, as the winding is wound, each turn thereof may be stretched along the inner surface between corresponding slots on opposing ends of the core. Each turn may therefore be accurately positioned along a precise path from end to end of the core. End turns are formed by extending each turn radially outward from the region enclosed by the core and along the outside surface of the core in an annular direction to another slot through which it is guided and again stretched through a precise path along the inner surface of the core to a corresponding slot on the opposite end of the core. The turn is then extended radially outward and along the outside surface of the core in an annular direction opposite to the direction of the end turn on the opposing end of the core in a manner commonly employed in winding saddle type coils. The process is repeated until a suitable number of turns have been wound on the core. The resulting winding comprises a plurality of turns wound directly on the core in a saddle-type configuration with each turn being accurately positioned along the inner surface of the core.

BRIEF DESCRIPTION OF THE DRAWINGS The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself. however, both as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. I shows, in section, an embodiment of the present invention as applied to a cathode ray tube;

FIG. 2 is a perspective. partially cut-away view of the deflection yoke shown in FIG. 1'. and

FIG. 3 is a perspective, partially cut-away view of an alternate embodiment of the deflection yoke core shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 depicts an embodiment of the present invention as applied to a color television picture tube 10. Cathode ray tube having a neck portion 12 and a base 14 contains an electron gun assembly (not shown) within the neck portion, which generates at least one electron beam directed away from the base. Surrounding neck portion I2 is a magnetic deflection yoke 16.

FIG. 2 is a perspective view of deflection yoke 16 of FIG. I, simplified for purposes of describing the invention. A yoke core 18 of suitable magnetic material, such as a magnetically soft ferrite of the type described by E. C. Snelling, Ferri'res for Linear Applications, 1- Properties, IEEE Spectrum, January, 1972, pages 42-51, is formed in the shape of a cylinder having a flared end adapted to fit around neck portion 12 of tube 10 and extend over a portion thereof. A first insulative ring 20 is attached to the flared end of core 18 as by a press fit or by use of an adhesive such as glue, and has formed therein a plurality of slots 22. A second insulative ring 24 is attached to the opposite end of core 18 in the same manner, and has formed therein a plurality of slots 26. It is to be understood that slots 22 and 26 extend substantially around the entire circumference of rings 20 and 24, respectively.

Normally in deflection yoke 16, there are located, on the neck of the tube, two windings diametrically opposite each other for horizontal deflection, with their centers situated on a vertical axis, and two windings diametrically opposite each other for vertical deflection, with their centers situated on a horizontal axis. Other windings, such as quadripole windings, may be distributed around the core. For the sake of clarity, only the top and bottom horizontal windings 28 and 30, respectively. and the right and left vertical windings 32 and 34 respectively. are shown. Although each of these windings is indicated as comprising only three turns, those skilled in the art will recognize that each of the windings may include many turns.

Since each winding is positioned and constructed essentially in the same manner, reference may be had to vertical windings 32 as exemplary of the windings in the embodiment of FIG. 2. Winding 32 includes essentially parallel segments or side conductors 38 and return segments or end turns 40 and 42. The term end turns" refers to all that portion of the windings other than the parallel segments inside core I8. Segments 38 are positioned within core 18 by stretching the conductors between corresponding ones of slots 26 and 22 such that each individual segment is directly positioned by both opposite walls of each slot of the corresponding ones of slots 26 and 22. End turns 40 and 42 leave segments 38 in a radial direction and are then bent or extended back over the outside surface of core 18. End turns 40 and 42 are made in the form of arcs extending from selected slots to selected slots of rings 20 and 24, respectively. Since the end turn crossings are characteristic of a saddle-type winding and are made in a location inward from the end of the coil, the flux associated therewith is far less effective in distorting the electron beam; if desired, however, end turns 40 and 42 may be formed as in conventional saddletype windings, i.e., at the ends of the radial extensions from segments 38 without bending or extending the end turns back over the outside surface of core 18, since the positioning of parallel segments 38 is of more importance in obtaining the advantages of a toroidal yoke in a saddle wound yoke.

By stretching segments 38 between respective slots in rings 20 and 24, accurate placement of the segments is facilitated. The degree of accuracy in making such placement has not previously been attainable in conventional saddle wound yokes. Since each turn of a winding is accurately positioned inside core 18, each turn can be accorded a relatively high magnetic weight" as is common for toroidal yokes. Conse quently, only a small number of turns are required, resulting in a saddle wound yoke having low impedance. In addition, the precise placement of each turn allows for better control of final beam impact position, a fea ture of extreme importance in plural gun color television picture tubes. If the slots are made sufficiently deep, more than one layer of conductors may be accommodated in each slot, one atop the other, with each conductor in the slot being directly positioned by both opposite walls of the slot.

Although rings 20 and 24 are conveniently formed with a plurality of slots 22 and 26 and are attached to respective ends of core 18, grooves or slots may alternatively be formed directly in the core at each end. Moreover, as shown in FIG. 3, core 18 may be fabricated having grooves or slots 36 formed on the inside surface thereof. In the embodiment of FIG. 3, each turn of a winding may be positioned by causing the first layer of turns to fall within slots 36 thereby assuring their accurate placement, each individual segment within any respective one of slots 36 being directly positioned by both opposite walls of the respective slot.

By forming the saddle-type winding directly on a core, yoke construction time is reduced since the number of steps in the construction process is reduced. For example, typical construction of a saddle-type winding presently used by the color television industry first requires a winding operation. This is followed by varnishing and baking the winding, followed in turn by forming or shaping the winding. Finally an assembly operation is performed in which the windings are attached to a support and a two-part core is placed around the windings and attached thereto by another support. In the present invention the yoke is brought to this completed status by the single operation of winding the coil directly on a core, thus resulting in considerable cost saving. The assembly operation as well as the forming or shaping step are completely obviated by these operations being completed essentially automatically as part of the yoke fabrication process, while the need to varnish and bake the windings is reduced because of the minimal handling required by the winding.

The foregoing describes apparatus for combining in a single magnetic deflection yoke the high sensitivity of a saddle-type yoke and the low impedance and accurate winding placement capabilities of a toroidal yoke. The single magnetic deflection yoke is capable of deflecting electron beams in a wide angle cathode ray tube without producing neck shadow, and concentrates magnetic flux in a relatively small volume. A method of fabricating a toroidal-like saddle yoke wherein the saddle-type winding is formed directly on a magnetic core is also described.

While only certain preferred features of the invention have been shown by way of illustration, many changes and modifications will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such changes and modifications falling within the true spirit and scope of the invention.

What is claimed as new and desired to be secured by letters Patent of the United States is:

l. A magnetic deflection yoke comprising:

a yoke core adapted to fit about a portion of a cathode ray tube; and

a saddle-type winding wound directly on said core,

said winding including a plurality of turns of a conductor having first segments positioned adjacent the inside surface coaxially of said core and having second segments extending outward from each end of said core and circumferentially around the outside surface of said core, each of said first segments having at least a portion thereof directly positioned by both opposite walls of a respective slot in said core.

2. The deflection yoke as defined in claim 1 wherein said second segments are folded back over each end of said core.

3. The deflection yoke as defined in claim 1 wherein said slots are contained in a pair of rings, each of said rings being attached to a separate end of said core. respectively.

4. The deflection yoke as defined in claim 1 wherein said slots are formed in each end of said core.

5. The deflection yoke as defined in claim 1 wherein said slots are formed on the inside surface of said core.

6. A magnetic deflection yoke comprising:

a yoke core adapted to fit about a portion of a cathode ray tube; and

a plurality of windings wound directly on said core,

each of said windings including a plurality of turns of a conductor having first segments positioned adjacent the inside surface coaxially of said core and having second segments extending radially outward from each end of said core, said second segments extending circumferentially around a portion ofthe outside surface of said core, each of said first segments having at least a portion thereof directly positioned by both opposite walls of a respective slot in said core 7. The deflection yoke as defined in claim 6 wherein said plurality of windings comprises a first and second pair of windings. said first pair being oriented with respect to said core to provide a magnetic field along a first direction and said second pair being oriented with respect to said core to provide a magnetic field along a second direction substantially perpendicular to said first direction. 

1. A magnetic deflection yoke comprising: a yoke core adapted to fit about a portion of a cathode ray tube; and a saddle-type winding wound directly on said core, said winding including a plurality of turns of a conductor having first segments positioned adjacent the inside surface coaxially of said core and having second segments extending outward from each end of said core and circumferentially around the outside surface of said core, each of said first segments having at least a portion thereof directly positioned by both opposite walls of a respective slot in said core.
 2. The deflection yoke as defined in claim 1 wherein said second segments are folded back over each end of said core.
 3. The deflection yoke as defined in claim 1 wherein said slots are contained in a pair of rings, each of said rings being attached to a separate end of said core, respectively.
 4. The deflection yoke as defined in claim 1 wherein said slots are formed in each end of said core.
 5. The deflection yoke as defined in claim 1 wherein said slots are formed on the inside surface of said core.
 6. A magnetic deflection yoke comprising: a yoke core adapted to fit about a portion of a cathode ray tube; and a plurality of windings wound directly on said core, each of said windings including a plurality of turns of a conductor having first segments positioned adjacent the inside surface coaxially of said core and having second segments extending radially outward from each end of said core, said second segments extending circumferentially around a portion of the outside surface of said core, each of said first segments having at least a portion thereof directly positioned by both opposite walls of a respective slot in said core.
 7. The deflection yoke as defined in claim 6 wherein said plurality of windings comprises a first and second pair of windings, said first pair being oriented with respect to said core to provide a magnetic field along a first direction and said second pair being oriented with respect to said core to provide a magnetic field along a second direction substantially perpendicular to said first direction. 